A fast, efficient and reliable means of communicating data in a multi-user system is desirable for many applications. A need for such methods arises when multiple pieces of data (from multiple sources) need to be quickly read by a receiver. One particular application of such technology is in the electronic identification of multiple items.
The electronic identification industry is important for numerous commercial and military applications, including real-time item tracking and inventory. Such uses can greatly increase operational efficiency in a myriad of scenarios, including virtually all of those involving some form of manufacturing, warehousing, distribution and retail. The ability to quickly and efficiently perform accurate real-time inventory tracking can greatly reduce waste in many forms, including, but not limited to, the misplacement of items, over- or under-stocking of items, and item theft.
Currently, the electronic identification industry relies heavily on manual (light-based) scanning to identify a plurality of items, where each item is assigned a product code. The Universal Product Code (UPC) system is currently in widespread use throughout the United States retail industry. Manually scanning items, however, is extremely time-consuming and highly prone to human error.
Thus, there exists a need to provide a method for fast, efficient and reliable transmission of data from multiple sources to a receiver. More specifically, there exists a need to read such data as quickly as possible for all possible operating cases in an RFID system. In order to maximize data communications throughput, a RFID system may utilize a very high symbol rate, high enough that it is an appreciable fraction of the RF carrier frequency. Reliable system operation must be preserved for these cases. In some low carrier frequency systems, as few as two RF cycles per symbol may need to be used in order to achieve the desired throughput. Such a high relative symbol rate system leaves little margin for timing error (especially for systems that rely on good symbol synchronization), emphasizing the necessity of a highly accurate synchronization method and apparatus.